John gardner



. m# mmm l. GARDNER.

SUBMARINE SOUND SIGNALING.

APPLICATION FILED JULY 31, 1911.

'l ,3 l 0,0 1 1 V Patented July 15, 1919.

JOHN GARDNER, 0F FLEETVVOOD, ENGLAND.

SUBMARINE SOUND-SIGNALING.

Application led July 311` 1917.

To all w71 om if ymuy concern lie it known that l. .lonx (lannxnn, of Knott llnd. Fleetwood. in (he county of lianaster. llngla'nd. a subject of George V, King ot' Ilng'land. have invented a new and useful Improvement i-n.and Relating' to Submarine Sound-Signaling. of which the following is aspecitication.

Thisl invention relates to a microphonic appliance for thereception. and amplification of sound vibrations. and is especially useful in submarine sound signaling. The principal objects of the invention are to so arrange such appliances that they shall be as fully l responsive as possibile, to arriving vibrations` and that an operator with a musical ear may simply and easiljiY tune an appliance t'or the reception otl any given sound.

A microphonic appliance in its preferred form constructed in accordalu-e with this invention comprises essentially an electrode rigidly att-ached to a support. the complen'lentary eoperating electrode heilig carried by a vih 'atory diaphragm properly supported in sucha way that it-s operative impulses are, received solely through the node formed hy `its pointof attzu'hmcnt. together with means for adjustably weighting the diaphragm to tune it. as may be desired. a. resistance-varying mediumluing arranged between the electrodes.

My invention will be understood by reference to the drawings in which it is shown in its preferred forms. t

Figure l is a longitudinal section of a device. embodying my invention.

' Fig'. 2 is a similar section o'l' a modilication in which two microphones are used.

Fig. 3 is also asimilar section of a modificat-ion in which the diaphragm member is supported at one end only. its other end being'free to vibrate.. and

Fig. 4 is a similar section of the device shown in Fig. 1 having an additional diaphragm as below described.

On the drawing and in the followingdescription like marks of reference indicate like parts.

Referring first to Fig. l of the drawing, a is the base to which one of the electrodes is attached. It is shown as the skin of the sound-receiving ship though it may be otherwise. It preferably has rigidly attached to it by screws c a easing' l). lVithinthc easino an electrode d is rigi ily secured parallelhto the skin a by a screw e so that it par- Specication of Letters Patent Patented July 15, 1919.

serial No. 183.813.

takes, wit-hout loss, of all vibrations affecting the skin (l. Surronmling or at either side of the electrode (l, the casing is provided with a .supporting ledge f to which a vibratory diaphragm y] clamped by a ring' L and screws k1. the support forming the `nodo or nodes of said diaphragm. The v-ibratory diaphragm ,1/ may be a circular disk, in which case the support f will be annular or of other suitable formation. Preferably the diaphragm f7 is in the form of a strip or reed. The diaphragm y has attached to it by means of a screw j and nut an eleetrode m adapted to cooperate with the electrode (Z with which it is electrically connected by means of carbon balls or granules or other suitable resistance-varying' medium n, preferably arranged in cup-like, depressions or cavities o in the vl'ace of the electrode m. The diaphragm f/ is weighted by a variable weight p screwed on the screw j.

0n receipt of sound vibrations the skin a and electrode Z rigidhv attached thereto are vibrated. The. diaphragmf/ is also vibrated, the vibrations, as just. stated. being' transmitted through its nodes and the inertia of its free portion to which theI electrode m is attached serves to bringabout. through the resistaruie-varying medimn n, the variations in electrical resistance between the electrodes d and m necessary to produce the desired etl'ect in a telephone with which the appliance is in circuit.

The diaphragm g is given a natural period of vibration correspoiuling to the distant sound Igenerator. This may be done by sultably arranging its length, thickness. or tension or the load carried by it, e., by varying the weight p. By the latter means an operator having ,a musical ear can simply and quickly tune the diaphragm to attain the .greatest amplitude lof vibration when it is subjected to a sound of the desired frequency.

Although I have described and illustrated the Strip or reed constituting the diaphragm g as being` supported at both ends and consequently having` two nodes through which it receives its operative impulses, it may be supported at one end only and be free at the other end and receive said impulses through a single node (see Fig'. 3).

The appliance first above described may be provided with a second diaphragm g3 not carrying an electrode. This additional diaphragm will be fixed parallel to and on the supports carrying the diaphragm g (see Fie. 4) by the screws L. The two diaphragms will be given different natural periods of vibration. For example the diaphragm g carrying the electrodes m may be tuned to a prominent Overtone'of a bell, Iand the additional diaphragmtuned to the fundamental not/e of the bell, the framework of the instrument, serving to convey the vibrations imparted t the additional instrument from the skin (l, to the electrode m on the diaphragm g. Y,

As a further modification (see Fig.V '2) the microphonie apparatus as first described may7 be duplicated, one set having its diapl agm timed to respond to a fundamental note and the diaphragm of the other set being timed to a prominent overtone. Both sets may he in the same telephone circuit, arranged in series or in parallel, .or otherwise and in ei-reuit with other apparatus such as may occur to one skilled in the art.

ln man v cases it is desirahle'to have in one instrument two microphones the diaphragms of which arel or can he timed to slightly (,liferent frequencies, that is, two fundamentals or two overtones. ln the modification `last described the diaphragms are tuned to different notes, namely, one-to the fundamental note and the. other t0 a prominent overtone of the distant sound generator. fllhe Vsaid modification operates satisfartorily if there is a wide or marked di ference iii the frequencies of the two diaphragnis, but if the latter are so timed that their frequencies are nearly alike, one diaphragm then too easily controls the other with the result that they compromise.on one frequency (the mean or approximately the mean of the two) and' thus give a single fundamental tone instead of two distant tones, oi' one overtone instead of two separate, overtones, notwithstamling that there are two microi'ihones. 'llo overcome this deieetl, in the said rases. employ a single diaphragm o't strip or reed form clamped to the snips skin or other base over a-la'rge part of its middle portion and unsupported at :both ends which are free to vibrate and `Carry electrodes which Coperatie"withl complementary eleetrodesrigidly secured to the shipls skin as before. -While there is thus only one diaphragm it'vibratesivith differ# ent 'frequencies at its two free ends, each `end being musically independent of the fotner.

The two microphones thus constituted nia-y, as before, be used separately, or they may be used in combination, e., in series or parallel. n

An embodin'ient of the modification just described vis illustrated in -Fig. 2 in Which r1, is the skin of the ship or other base and o acasing rigidly attached thereto as before.` The casing is provided vWith'a projecting support f which forms the node of the strip or reed diaphragm y and also the pathnfor transmitting the vibrations from the skin a to the diaphragm f/ which is clamped to the support f by a clamping plate z and screws t. The diaphragm g and the node-forming support f' are .of such relative length that. the ends g, (/2 of the diaphragm` extendbeyond the endsl of the support and'are free and the diaphragm is in contact with and clamped to the support over a large partl of its middle portion. The free ends fj?, y of the diaphragm carry electrodes m, n.2 adapted to coperate through resistance-varying me.- diuin a with complementary electrodes fl, J2 rigidly secured to the casing parallel 1to the skin a. The screws which sei-ure the` electrodes m1, Am2 are, as before. adapted to receive variable weights )i for timing the ends [/1, r/2 of the diaphragm y/ to. adjust the natural periods thereof to the distant souiid generator so that"amplification may be\ secured for the desired sound with corresponding choking of undesired sounds'.

ln the improved'instrument just described and also in those instruments previously described wherein the end or ends of the diaphragm is or are free, I prefer that the said free end or' ends should extend beyondt-he middle of tliefelectrode or electrodes carried by it ort-hem so that the electrode or elec.- trodes is or are nearer the middle than the extremityv or extremities of the-free end or ends of the diaphragm.

I also prefer to employ aluminum or aluminum alloy as the material of the diaphragm'. The lightness of this material .facilitates the attainment of the high fre'- queneies often required.

Further, When 'one lof the electrodes or one of each pair of eoperating electrodes is of cup-like forn'iation or provided with cavities or depressions ofo'r the retention of thel resistance-varying medimn n, I prefer that suchv` electrodes should-'be that vof those carried by the diaphragm in order that the slope of the ships plating may not cause said medium to retire into the cup, cavities or depressions, and possibly break the eircuit altogether. f While the above invention is particularly adapted for attachment to the side or skin of ay ship, the deVice may be otherwise supmicrophonic instrument comprising an electrode,"a sound-receiving wall, said electrode being rigidly connected thereto, a diaphragm, a second electrode mounted therei 'on in electrical contact with said first elec' trode, a support for said diaphragm also connected to said vsound-receiving wall,

whereby the sound wavesimay be conveyed thereto and the electrode mounted thereon will be given a greater amplitude of vibration than said first electrode.

2. In a device of the kind described, a microphonic instrument comprising an elec- A trode, a sound-receiving wall, said electrode being rigidly `connected thereto, a diaphragm, a second electrode mounted thereon in electrical contact with said first electrode,

la support for said diaphragm also connected to said sound-receiving wall whereby the sound Waves maybe conveyed thereto and theelectrode mounted thereon will be given a greater amplitude of vibration than said iirst electrode, and means whereby the diaphragm may be tuned to -a desired frequenc 1 3. n a devlce of the kind described, two

diaphragms and a single means for support- .ing themun operative relation with each other, one diaphragm being' tuned to the fundamental tone andy the otherto a lprominent overtone of the -`sound'to be received,

and a microphone one element of which is mounted on one of said diaphragms, the

for one element of each microphone, and af vibratory support for the other element of each microphone, said vibratory support compri'ng diaphragms, one diaphragm being tuned to a fundamental tone :1nd the other diaphragm being tuned to a -prominent overtone of the sound to be received.

JOHN GARDNER. 

